KYIV/WARSAW/MOSCOW - Representatives of Europe will take part in peace negotiations between Ukraine and the United States on Friday, Ukraine's top peace negotiator Rustem Umerov said.

"Today in the United States, together with Lieutenant General Andrii Hnatov, we will begin another round of consultations with the American side. At the invitation of the US side, European partners are also involved in this format," Umerov wrote on social media.

He added that the Ukrainian delegation has already held preliminary consultations with European representatives and is preparing for further discussions with the US side.

Umerov emphasized that the Ukrainian team remains committed to a constructive process and will act in line with the priorities set by Ukrainian President Volodymyr Zelensky, including the need for reliable long-term security guarantees for Ukraine.

ALSO READ: Ukrainian delegation en route to US for peace talks

Battlefield situation 'complicated'

Zelensky, who is on an official visit to Poland, said on Friday that the situation on the battlefield is complicated and increasingly difficult.

He told the media that he recently visited Kupyansk, a key transport hub in eastern Ukraine's Kharkiv region, depicting the situation there as challenging with the front line very close.

Despite pressure exerted by Russian forces, Zelensky said Ukrainian forces remain in control of the city.

Meanwhile, during his annual press conference on Friday, Russian President Vladimir Putin said that Kupyansk "came under our control several weeks ago", and that about 3,500 Ukrainian soldiers were encircled near the city.

Zelensky also said there had been "problems with the availability of certain types of ammunition and air defense missiles for various reasons, and deliveries were also delayed". But he noted that this is not an accusation directed at Ukraine's partners.

Bolstering cooperation with Poland

During the visit to Poland, Zelensky and Polish President Karol Nawrocki reiterated their cooperation on security at a joint press conference in Warsaw. 

Underlining that Poland has been providing staunch support to Ukraine since 2022, Nawrocki said that promoting lasting peace is in the common interest of Poland, Ukraine and Europe as a whole.

At the same time, Nawrocki said Poles feel that their country's assistance to Ukraine has not been met with sufficient appreciation and understanding.

This kind of "general atmosphere" is reflected in public opinion polls, Nawrocki said, adding that he had conveyed this in a firm, honest, but very cordial and gentlemanly conversation with Zelensky. He noted that authorities in Kyiv currently have the tools to curb and reverse this sentiment and trend.

In addition, Nawrocki highlighted the two countries' willingness to work together on liquefied natural gas terminal projects, with the aim of turning Poland into an energy hub for Central and Eastern Europe.

Visiting Poland for the first time since the inauguration of Nawrocki in August, Zelensky thanked Poland for its long-standing support and stressed the importance of maintaining strong bilateral ties, saying he hoped that the visit would mark a turning point in ties between Warsaw and Kyiv.

ALSO READ: Report: US, Russian negotiators to meet in Miami on Ukraine crisis

He said Ukraine is willing to consult with Poland on drone defense, and is ready to cooperate on maritime security, adding that he had invited Nawrocki to visit Ukraine to see the country's defense manufacturing capabilities. Zelensky also invited Polish companies to take part in Ukraine's post-war reconstruction.

Ball in court of Ukraine and its European sponsors

In another development, Russian President Vladimir Putin said Russia agrees to resolve the Russia-Ukraine conflict through negotiations and "the ball is entirely in the court of Ukraine and its European sponsors."

Russia practically agreed with US President Donald Trump's proposals on the Russia-Ukraine conflict during their meeting in the US state of Alaska, Putin said at the annual year-end press conference.

"To say that we reject anything is absolutely incorrect and has no basis," he said.